Mageia2 on EC2: Stormy Weather

This is my third post on getting Mageia2 running on Amazon Web Services' Elastic Compute Cloud. See my first post in the series for an overview.

In my last post I described how to create and upload an AMI that allows you to run Mageia2 on EC2. There were two issues with that method:
  1. The EC2 instances are using a one-off unverified kernel, obtained for testing purposes only.
  2. The instances launched can only be instance-store backed, ephemeral disk.
Both of these problems are solvable. We'll address the kernel first. The solution? Compile your own!

As with any good open-source project, you can easily obtain the source code. The same holds for Mageia. For recompiling the kernel, I plucked the kernel's SRPM file off mirrors.kernel.org. Reviewing the source, there were considerable tweaks made by the Mageia development team - so much so that they were bundled together inside the SRPM. Once I was able to dig into that tarball, I found where to enable CONFIG_KERNEL_GZIP and disable CONFIG_KERNEL_XZ in the configuration.

Now it was a matter of getting a system to build the kernel on. Initially, I tried to do it on my local seed Mageia VM, but the 10GB disk was too small to hold all the compiled kernel sources. So, I launched an instance using the EC2 console of the freshly-uploaded Mageia2 AMI. This is where I ran into the limitation of the first revision of the AMI I created - 2GB was insufficient to install all the compiler dependencies needed for creating a kernel package - but 8GB was ok.

Finally, I launched an m2.xlarge instance via the EC2 console with an 8GB root disk on instance-store to do the compilation. I wanted an instance with at least 2 cores to speed up the compile and sufficient additional space on ephemeral disk (/dev/xvdb) that could hold the compiled kernel sources. It still took a considerable amount of time - approximately 2 hours to compile the RPM. When I have to do this again in the future, I might consider a high I/O instance to reduce the time spent waiting for the compile. Either way, the cost is negligible if you remember to shut it down after you're done - the m2.xlarge was around $1.35 for 3 hours and a hi1.4xlarge would be $3.10 for one hour. For those who follow this blog, you should recognize the build script.

EDIT: on 1/18/13, I recompiled the kernel using an hi1.4xlarge and the final timing from "time ./do-build.sh" was:

real    51m5.356s
user    173m1.470s
sys     32m44.040s

Of course, it took a little longer than that to install all the packages needed for building, but it can be done in less than 2 hrs.

Here are the steps for compiling the Mageia2 kernel:

# prep stuff done as root
sudo bash -o vi
# mount the ephemeral storage
mkfs -t ext4 /dev/xvdb
mkdir /media/extra
mount /dev/xvdb /media/extra
# create some swap
dd if=/dev/zero of=/media/extra/swapfile00 bs=1024 count=4194304
mkswap /media/extra/swapfile00
swapon /media/extra/swapfile00
# setup space for kernel building
mkdir /media/extra/kernel
chown $USER:$USER /media/extra/kernel

# build stuff done as normal user
# prep for kernel building
cd $HOME
ln -s /media/extra/kernel
cd kernel/
# bring down the source
curl -O http://mirrors.kernel.org/mageia/distrib/2/SRPMS/core/updates/kernel-3.3.8-2.mga2.src.rpm
# extract the source
rpm2cpio ../kernel-3.3.8-2.mga2.src.rpm | cpio -i
# make a working copy of the .spec file
cp -p kernel.spec ..
# extract the mageia customizations
tar Jxf linux-3.3.8-mga2.tar.xz
cd 3.3.8-mga2/configs/
# modify the kernel config for gzip compression
cp -p x86_64.config x86_64.config.orig
vi x86_64.config
# diff of what it looks like when it's done
$ diff -u x86_64.config.orig x86_64.config
--- x86_64.config.orig  2012-07-12 08:53:47.000000000 +0000
+++ x86_64.config       2012-11-15 04:48:37.000000000 +0000
@@ -67,10 +67,10 @@
-# CONFIG_KERNEL_GZIP is not set
 # CONFIG_KERNEL_BZIP2 is not set
 # CONFIG_KERNEL_LZMA is not set
+# CONFIG_KERNEL_XZ is not set
 # CONFIG_KERNEL_LZO is not set

# rebuild the mageia customizations
cd ../..
mv linux-3.3.8-mga2.tar.xz linux-3.3.8-mga2.tar.xz.orig
tar Jcf linux-3.3.8-mga2.tar.xz 3.3.8-mga2

# install builder dependencies
sudo urpmi easyrpmbuilder
sudo urpmi elfutils-devel zlib-devel binutils-devel newt-devel python-devel pciutils-devel asciidoc xmlto docbook-style-xsl

# setup the build script
cat do-build.sh
#!/bin/sh -x

OPTS="$OPTS --with=server"
OPTS="$OPTS --without=desktop"
OPTS="$OPTS --without=desktop586"
OPTS="$OPTS --without=netbook"
rpmbuild $OPTS -bb --define="_topdir $PWD" --define="_tmppath $PWD/tmp" kernel.spec 2>&1 | tee kernel-build.txt

# do the build
time ./do-build.sh

# save the rpm
scp -p RPMS/x86_64/kernel-server-3.3.8-2.mga2-1-1.mga2.x86_64.rpm $REMOTE_SERVER:

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